The spatiotemporal characteristics of neural substrates of involuntary attention switching elicited by an unattended auditory change (deviant), and the relationship of this process to automatic (passive) and active change detection, will be investigated in two experiments using simultaneous ERP/fMRI. In a first experiment, the difficulty of a primary task in a selective attention paradigm will be varied in order to modulate the rate of attention switching to task-irrelevant rare auditory change. A comparison of the ERP and the BOLD responses to rare auditory deviants in each condition is expected to reveal the temporal and spatial characteristic of neural generators involved in involuntary attention-switching and change detection. In a second experiment, a divided attention paradigm will be used to compare ERP and BOLD responses to auditory change that do and do not elicit subsequent active detection of the deviant auditory event. This comparison is expected to yield information about the relation between involuntary attention switching and active deviant detection. The automatic detection of auditory change is hypothesized to involve predominantly auditory regions of the temporal cortex, whereas involuntary switching of attention and overt detection of the deviant event are thought to engage mainly structures in the dorsal and ventral prefrontal cortices, respectively. [unreadable] [unreadable]